In order to investigate the role of various surface proteins from the bacteria B. pertussis in the mechanism of attachment of the whole bacteria to mammalian cells, mutants have been constructed which do not express specific proteins normally localized on the surface of the bacteria. By use of antibiotic markers and double recombination events, mutants deficient in the expression of pertactin, FHA or both proteins have been constructed. We have characterized these mutants in terms of the expression or lack of expression and activity of various proteins including pertactin, FHA, pertussis toxin, adenylate cyclase, fimbriae, and olipooligosaccharide. We have also characterized these mutants in terms of their ability to promote cell attachment. A decrease in the ability to adhere to mammalian cells has been seen with all three mutants, and a synergistic effect of decrease adherence is observed with mutant lacking both pertactin and FHA. With the use of the pertussis suicide vector pRTP1, mutants lacking the expression of pertussis toxin and other virulent associated proteins are being constructed to determine their possible role in bacterial adherence.